Objective   To detect the dual-labeled Aβ42 and miR-388-5p in exosomes of nerve cell adhesion molecule (NCAM) and ATP binding cassette transporter A1 (ABCA1), and analyze their potential value in the early diagnosis of Alzheimer's disease (AD).

  Methods   The levels of plasma NCAM/ABCA1 exosomes Aβ42 and miR-388-5p of 67 cases of subjective cognitive decline (SCD), 65 cases of amnestic mild cognitive impairment (aMCI), 68 Alzheimer's disease cases with dementia (DAT), 60 healthy controls and 60 controls of vascular dementia (VaD) cases were detected, and the correlation between the indicators and the diagnostic power of each disease stage were analyzed.

  Results  The plasma levels of NCAM/ABCA1 double-labeled exosomes Aβ42 in SCD, aMCI and DAT cases were significantly higher than those in controls of VaD cases and healthy controls (P<0.05). In plasma NCAM/ABCA1 of SCD, aMCI and DAT cases, the content of miR-388-5p in double-labeled exosomes was significantly lower than those of controls of VaD cases and healthy controls (P<0.05). The sensitivity and specificity of plasma NCAM/ABCA1 double-labeled exosomal Aβ42 for SCD, aMCI and DAT were higher than those of miR-388-5p.

  Conclusion  This study suggests that Aβ42 and miR-388-5p in NCAM/ABCA1 double-labeled exosomes can be used as candidate markers for the diagnosis or early warning of aMCI and SCD, but longitudinal multicenter studies are still needed to further confirm the results.